Dr. Ricardo Samson is an Assistant Professor in the Department of Pediatrics and Steele Memorial Children's Research Center at The University of Arizona. During fellowship training, Dr. Samson acquired a research background in the area of cellular electrophysiology. However, given the advances of molecular biology techniques, Dr. Samson is seeking support to re-direct his research emphasis in molecular biology to pursue investigations in the development of the cardiac conduction system. The Steele Memorial Children's Research Center is a state-of-the-art multidisciplinary research institute with a particular emphasis in molecular biology that is capable of providing Dr. Samson with the environment necessary to flourish in this field. The electrophysiological properties resulting in rhythmic cardiac contraction have been well studied. Yet, the genes responsible for contraction are not completely defined. To understand the molecular mechanisms resulting in cardiac contraction, it is necessary to identify the genes involved and characterize their expression, function and regulation. Our hypothesis is that the L-type calcium channel (LCC) is crucial to the development of the beating heart in chick embryos and that the appearance of functional LCC is central to the development of the central conduction system. Hence, our approach to identify genes important in this development is directed at the LCC subunits- alpha1, alpha2, beta, gamma, delta. The genes encoding the LCC subunits have been reported in other species but not in the chick. Heart development has been best characterized in chick embryos. Our specific aims are to: (1) Clone the chicken specific LCC subunits using degenerate oligonucleotide strategy. We have already successfully cloned and sequenced a gene fragment for the chicken alpha1 subunit. (2) Perform a developmental survey of LCC gene expression using RT-PCR analysis of embryonic chick hearts at various developmental stages. (3) Determine the quantitative spatial and temporal expression patterns in embryonic chick heart, using ribonucleic acid protection assay analysis and situ hybridization. We will have thus determined the developmental stage at which intact LCC are expressed. (4) Determine the full length DNA sequence of each LCC subunit. Our overall objective is to characterize the expression pattern of LCC in chick heart development and to correlate this with the appearance of cardiac contraction and the establishment of the central conduction system. It is expected that the data resulting from this proposal will lead to further mechanistic studies that will form the basis for application for an RO-1 award from the NIH.